1. Field of the Invention
The present invention relates to a 5-aminopyrazole-4-carboxylate derivative which is an important intermediate of medicines and agricultural chemicals, and process for preparing the same. For example, ethyl 5-amino-1-methyl-3-trifluoromethylpyrazole-4-carboxylate can be prepared by the process of the invention and can be converted to a useful intermediate for agricultural chemicals, ethyl 1-methyl-3-trifluoromethylpyrazole-4-carboxylate (Japanese Laid-Open Patent Hei 1-106866), by diazotization and successive elimination of amino group according to a known technique.
2. Prior Art
Various compounds having a pyrazole skeleton have been known as medicines, agricultural chemicals and fungicides in particular. Accordingly, it has been strongly desired to develop a process for efficiently preparing the compounds having the pyrazole skeleton. Particularly, 5-aminopyrazole-4-carboxylate derivatives are important intermediates for preparation in the field.
Conventionally, various preparation processes have been known for the 5-aminopyrazole derivatives. For example, Japanese Patent Gazette Hei 6-503069 has described a process for preparing various 5-aminopyrazole derivatives by condensation of a cyanoalkenyl compound represented by the formula (5): ##STR2##
wherein L is a C1 to C4 alkoxy group, R.sup.5 is a hydrogen atom or an unsubstituted or halogen substituted C1 to C4 alkyl group, and R.sup.6 is cyano group, --CO--R.sup.7 group or --CS--R.sup.7 group, wherein R.sup.7 is a hydroxy group, C1 to C4 alkoxy group, amino group, C1 to C4 alkylamino group or di (C1 to C4)alkylamino group, in the presence of a base with a hydrazine compound represented by the formula (6): ##STR3##
wherein R.sup.8 is a phenyl group which can be substituted with a C1 to C8 alkyl group or C1 to C8 hydroxyalkyl group having no substitution or further substitution with 1 to 3 halogen atoms, nitro group, C1 to C4 alkyl group, partially or wholly halogenated C1 to C4 alkoxy group, C1 to C4 alkylthio group or --NR.sup.9 R.sup.10 groups, wherein R.sup.9 and R.sup.10 are hydrogen atoms or C1 to C4 alkyl groups, and the phenyl group can additionally have totally 4 or 5 halogen atoms.
J. Heterocycl. Chem. 12 1199-1205 (1975) has reported a process for preparing a 4-cyano-5-aminopyrazole derivative according to the following reaction formula (A): ##STR4##
wherein R.sup.11 is a phenyl group, p-substituted phenyl group or p-substituted benzyl group and R.sup.12 is a hydrogen atom, a methyl group or hydroxyethyl group.
In these processes, the cyanoalkene derivative used for condensation with the hydrazine derivative is a .beta.-alkoxyacrylonitrile derivative.
The example of a substituent other than an alkoxy group on the portion L (eliminating group) in the formula (5) has been described in Zh. Org. Khim. 17, No. 2, 268-272 (1981). In the report, 5-aminopyrazole-4-carboxylate has been prepared according to the reaction formula (B): ##STR5##
5-Aminopyrazole-4-carboxylate derivative is prepared by chlorinating an alkali metal salt of 3-hydroxy-2-ene-carboxylate with phosphorous pentachloride and successively reacting the resultant 2-chlorocyanoalkene derivative with a hydrazine derivative. In the process, isomers of the aminopyrazole derivative tend to form.
As mentioned above, the known process for preparing the 5-aminopyrazole-4-carboxylate derivative uses an alkoxy group or chlorine atom for the eliminating group, and thus excessive steps are required for preparing the raw material cyanoalkene derivative.
Consequently, the object of the present invention is to provide a novel preparation process of 5-aminopyrazole-4-carboxylate derivative which can be efficiently carried out with ease in industry and has a low tendency to form isomers and a novel 5-aminopyrazole-4-carboxylate derivative obtained by the process.